Box-staying unit

ABSTRACT

A former block for applying stay paper to successive box blanks on a box former is alternately advanced towards and withdrawn from a corner edge of the latter. A device for feeding stay paper in front of the former block is drivably connected to said former block through a one-way drive and an adjustable lost-motion device. The one-way drive ensures that stay paper is fed during the withdrawal only of the former block and the setting of the lost-motion device determines the length of stay paper fed during each withdrawal. A stay-paper-severing device is actuated by engagement with the box former during the last part of the advance of the former block to sever the previously positioned length of stay paper before it is applied to the blank.

United States Patent 1 1 3,552,279

I 72] Inventor Arthur George Turner 5 References Cited [21 I A I No glam UNITED STATES PATENTS [22] ff 1 1968 2,722,166 11/1955 Keller 93/41 [45] Patented Jam 5:197! 2,982,188 5/1961 von Hofe et al 93/4] (73] Assignee Andrew 8: Suter Limited Primary Examiner-Bernard Stickney St. Albans, Herttordshire, England A/lorney-Woodhams, Blanchard and Flynn [32] Priority Sept. 7, 1967 [33] Great Britain [3i No. 40,997/67 ABSTRACT: A former block for applying stay paper to successive box blanks on a box former is alternately advanced towards and withdrawn from a corner edge of the latter. A device for feeding stay paper in front of the former block is drivably connected to said former block through a one-way drive and an adjustable lost-motion device. The one-way drive ensures that stay paper is fed during the withdrawal only of the [54] BOX-STAYING UNIT former block and the setting of the lost-motion device determines the length of stay paper fed during each withdrawal. A

8 Claims, 7 Drawing Figs.

52 us. (:1 93/41, y-p p i g d i is actuated y engagement with the 93/56 box former during the last part of the advance of the former [51] Int. Cl B3lb 1/72 l k to sever the previously positioned length of my p p [50] Field of Search 93/4 I, 56 before it is applied to the blank.

PATENTED JAN 5191:

SHEET 1 OF 3 INVENTOR.

ARTHUR GEORGE TURNER $1M Wg P mToR'Nevs NVENTOK AKTHUR Gtome TURNER Anoauevs SHEET 3 OF 3 mm m mi PATENTEU JAN 5 l9?! BY W WMAMSBIMLMJ 39 m BOX-STAYING UNIT This invention relates to an improved box-staying unit for use in box-making machines of the kind comprising a box former adapted to support, one at a time, a succession of box blanks, each having a middle portion which is to form the top or bottom of the finished box and flaps projecting from the edges of this middle portion, and so-called breaking means for converting the box blank into a folded box blank by bending the flaps to form sidewalls with juxtaposed edges which, after being stayed, will form the corner edges of the finished box.

Box-making machines of this kind are usually provided with four identical boxstaying units which are arranged to operate simultaneously to stay the four corner edges of each successive folded box blank while it is supported by the box former in a corner-stay-applying station. Each box-staying unit either incorporates, or is arranged to operate in conjunction with, means for withdrawing from a supply reel or the like a predetermined length of stay paper corresponding to the height of thecorner edge to be stayed and for feeding this length of stay paper into position to enable it to be applied by the staying unit to the corresponding corner edge of the folded box blank. Means must also be provided for severing each predetermined length of stay paper from next length which will be fed into position prior to the staying of the next folded blank. The stay paper used for such boxstaying is coated, on the surface thereof which is applied over the corner edge of the folded box blank so that it can be applied quickly and effectively by a heated former block which is an essential part of the staying unit.

In a known box-making machine of the kind referred to, the required predetermined lengths of stay paper are applied by the box-staying units to the corner edgesof each successive folded box blank at the corner-stay-applying station while these lengths of stay paper are still connected to the stay paper on the supply reels. The blank is then advanced to a stappaper-severing station, causing further predetermined lengths of stay paper to be withdrawn from the reels and brought into position for the corner-staying of the next folded box blank. In this known machine, the severing of the stay paper is effected by cutting-off devices which are arranged to sever the stay paper at each corner of the blank at a position immediately below the level of the bottom edges of the sidewalls.

The speed at which this known machine can operate is limited by the fact that the stay paper isnot severed until the box former and folded box blank, after the staying operation has been completed at the corner-stay-applying station, have been advanced and brought to rest at the stay-paper-severing station. Moreover, the pull exerted on the stay paper by the advance ofeach successive stayed blank from the corner-stayapplying station to the stay-paper'severing station can result in breakage of one or more of the strips of stay paper which in turn will cause a serious delay in the operation of the machine.

An important object of the present invention is to provide an improved box-staying unit and method whereby these disadvantages are substantially reduced.

According to the present invention there is provided a boxstaying unit for use in box-staying machines of the kind referred to, in which a former block having a Vee-groove in its working face and provided with heating means is arranged to be alternately advanced towards and withdrawn away from a corner edge of a folded box blank supported on a box former at a corner-stay-applying station. This box-staying unit is characterized in that it comprises stay paper-feeding means arranged to be operated by and during the withdrawal movement of the former block to feed a'predetermined length of stay paper from a supply of stay paper on a reel or the like into a position in front of the working face of the former block and extending from one end thereof in a direction parallel to the Vee-groove therein and stay-paper-severing means carried by the former block adjacent said one end thereof and arranged to be actuated, to sever the predetermined length of stay paper from the supply of stay paper, by engagement of a forwardly spring-loaded part of said severing means with the box former during the last part of the advance movement of said former block shortly before the former block applies the predetermined length of stay paper to the corner edge of the box blank, causing it to adhere to the latter under the combined action of heat and pressure.

The stay-paper-feeding means preferably 'in'cl'udesa staypaper-feed roller and a transmission which includes an adjustable lost motion device and a one-way driving gear, such as a pawI-and-ratchet drive, adapted for rotating'said feed roller during the withdrawal movement only of the former block, the arrangement being such that, during a first part of each withdrawal movement of the former block having a length dependent upon the setting of the lost-motion device, lost motion is taken up by said lost-motion .device so that no rotation is transmitted to the feed roller and, during the remainder of said withdrawal movement, the former block is drivably connected through said one-way driving gear to said feed roller, so that the latter is rotated to feed up a predetermined length of stay paper proportional to the length of said remainder of the withdrawal movement.

The adjustable lost-motion device may consist of a bar mounted for sliding movement in a stationary part of the staying unit, constantly biased by resilient means in the withdrawal direction of the former block, said bar being formed adjacent one end thereof with a longitudinal slot engaging over the shaft of the feed roller and having at its other end an abutment surface adapted to cooperate with a stop mounted in said stationary part so as to be adjustable towards and away from said shaft, and the said bar being further provided with a toothed rack meshing with a pinion forming the drive input element of said one-way driving gear. In the case where the one-way driving gear includes a pawl-and-ratchet gear, the said pinion may be fixed for rotation with a rotatable plate carrying the pawl of said pawI-and-ratchet gear.

The stay-paper-severing means preferably includes a cutting edge located directly adjacent one end of the former block and flush with the grooved working face of the latter and a further cutting-edge extending along the front of a transverse slot in a bar mounted for limited sliding movement relatively to the former-block in directions parallel to the advance and withdrawal movements of the latter, said bar being resiliently biased in the'advance direction of said former block and having an abutment edge for engaging the box former shortly, before the stay paper is applied to the corner edge of the folded box blank thereon. In this case, the stay paper will, in operation,be fed upward through the transverse slot and, after the slotted-bar has been brought to rest by engagement with the box former, the subsequent advance of the former block will cause the two cutting edges to cooperate to sever the stay paper.

The transverse slot in the slotted bar is preferably Veeshaped with the line of symmetry of the Vee-coincident with the longitudinal centerline of that surface of the slotted bar which contains the respective cutting edge,and the angle enclosed between the two arms of the Vee greater than that between the walls of the Vee-shaped groove in the working face of the former block.

A slotted guide for the stay paper may be removably mounted in a stationary part of the staying unit so that it can be replaced as required by like slotted guides of different widths for use respectively with different widths of stay paper.

The invention will now be described by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a box-staying unit, with its former block in the fully withdrawn position;

FIG. 2 is a corresponding plan view;

FIG. 3 is a fragmentary side elevation from the same viewpoint as FIG. 1, except that the former block is shown in a position towards the end of its advance movement,

FIG. 4 is a perspective view of an interchangeable staypaper guide member;

FIG. 5 is a fragmentary plan view ofa slotted knife. and

FIG.6 is a fragmentary side elevation from the same viewpoint as FIG. 1 illustrating modifications necessary to enable VII-VII in FIG. 6.

v The staying unit illustrated in the drawings has a rigid body .11 provided with-a base flange 12 which is adapted to be secured by screws or the liketo the frame of a box-making machine (not shown). This box-making machine has a vertically-movable former. block 9 which is arranged to bring a v folded box blank'13 into a position level with the staying unit to enable the latter to apply an adhesive coated staying strip along a vertical corner edge of the blank 13 for securing the jointbetween the adjacent edges of two side pieces thereof. The staying'unit illustrated may beone of four staying unit's provided on the box makingmachine in positions opposite the four vertieal'corner edges respectively of'the box blank l3 and arranged to'operatesimultaneously for the purpose of applyplungerl7.-which'is supported for'axial movement in bearings (not shown) in bearing housings l9 formed as integral parts of the body l I; is preventedfrom rotating by-akey rib 2 1 which.

' is slidablyguided in grooves (not shown) in the bearing housings 19..

Mounted on'the; end of the plunger remote from the -cylinder I4 is a plate 2210 which is secured a heat-sealing block 23 containing an electrical heating element24. The

working face of the block 23 is formed with avertical groove. 25, the twosidewalls of which are inclined to'each other at an.

angle-M90 asshown in FIG. 2. I i I i The lower end partof the plate 22 is secured by a bolt 26 to the sidewalls of a housing 27.;

' The pneumatic cylind'e'r,l4isadapted, 'when air is supplied I to it under pressure, to force the plate 22, together with the block'23and the housing 27 towards the left as seen in FIGS. 1 v t to '3. Means (not-illustrated) are provided for' releasingair from the 'cylinde.r l4, whereupon the plate 22,, together with the block 23 and the.ho'using 27, are returnedtowards the right as seen in FIGS. 1 to 3 by tension springs 20 conn'ected between the 'plate 22 and a part 10 of the body 11 of the stayingunit; v y

Q Mounted for horizontal sliding'rno'verrient in the housing 27 directly beneath a knife b'lade 28 fixed on the lower end of the block 23.is' a'slotted knife 29. The. knife blade 28 has two paper. 40 is passed through a slotted guide member 39 removably mounted in a slot in the body I] and then over a the unit to be used for staying so-called flanged box blanks. and FIG. 7 is afragrnentary horizontal section on'the line roller 41 rotatably mounted on a pincarried by lugs 42 on the body 11. After passing over the roller 41. the stay paper passes between the lower end part of an upper resilient metal guide strip 43 and the near upper end part 44' of a lower resilient metal guide strip 44 which guide it so that it passes round the lower part of the circumference of a feed roller 45. The lower guide strip has a flattened lower part 44" which is secured by screws (not shown) to the bottom of the housing 27. Between the rear upper end part 44" and the flattened lower part 44" of the guide strip 44 is a curved part of the latter which fits closely around the circumference of the feed roller 45. A similar curved part is provided on the forwardly extending side .ofthe lower guide strip 44 between the flattened part 44" and I a bracket 46 on the front upper end part of the said strip 44.

I This bracket supports a fgeelygotatable counterroller 47 which presses the stay strip 44 against the front part of the feed roller 45, partly due to the resilientaction of the front part of the strip 44 and partly due to that of two tension springs 48 (one of which .is shown in FIG. I) connected between the axis pin 49 of the counterroller 47 and a pin 50 i mounted in transverse boresin the housing 27. The stay paper is corrugated as it passes upwards between the roller 45 and the counterroller 47. This stiffens the paper, allowing it to pass firmlythrough the slot in the slotted knife 29 and ensuring that the portion above the latter will project vertically upward.

The length of stay paper left projecting above the slotted knife 2 9'after each feeding operation of the feed roller depends on the setting ofa control knob 51. This control knob 51 constitutes the head ofa screw 52 which is engaged in a screwthreaded bore in the body 11 and is provided with a locknut .53. The front end of the screw 52 acts as a stop to limit the extend of rearward movement of a sliding bar 54. A tension spring 55 connected between a projection 56 on the body 11 and a laterally projecting pin 57 On the sliding bar 54 constantly urges the latter to move rearwardly. The sliding bar 54, which is slidably mounted in a guide member 58 fixed to the body It and is slotted at 59 to fit over a sleeve rotatably mounted on the spindle 60 of the feed roller 45, carries a toothed rack 61. The sleeve just referred to is formed in- I tegrally with a pinion 62 and a pawl-carrying plate 63. On the pawl-carrying plate are mounted a pawl 64 which cooperates with a ratchet wheel 65 fixed on the spindle 60 of the feed roller 45, and a leaf spring 66 which resiliently urges the pawl a 64 towards the ratchet wheel 65. Integrally formed with the cutting edges which are inclined at right angles to each other,

and are flush'with th'e'two sidewalls respectively of the vertical I groove 25 in the block 23. Projectingfr'orn the rear edge ofthe slotted'knife'29are'two pins 31 which are slidablein guide I sleeves 32 fixedv to and rigid with the housing 27. Springs 33 surroundingtheparts of the pins' 31 between the rear end'of the slotted knife 29 and the front ends of the guide sleeves 32 constantly urge the slotted knife 29 forward with respect to the housing 27. Only one of each of the pins 31, hearing sleeves 32 and springs33 are visible in FIG. 1. The leading end of the slottedknife 29 is formed with a Vee-notch 34, the walls of which are at right angles to each other. Close behind this Vee-notch 34 is located the slot 35 of the slotted knife which is Vee-shaped, the two arms of the Vee being at an angle of approximately 160 to one another. The front edges 36 of the two arms of the Vee-shaped slot 35 are formed as sharp cutting edges for cooperation with the cutting edges on the knife blade 28 which is fixed to the block 23.

Two springs (not shown.) mounted in bores (not shown) in the front end part of the housing 27 constantly urge the slotted knife upwardly into close contact with the knife blade 28.

A supply of stay paper coated with a thermoplastic adhesive is carried on a reel 37 removably supported on an arm 38 bolted to the 11 body of the unit. From the reel 37, the stay flat base 68 (FIG. 4) with an inclined lead-in ramp 6) formed by an extension on its inlet end. The lateral margins ofthe flat ratchet wheel 65 is a knurled knob 67 for manually rotating the spindle 60, ratchet wheel 65 and feed roller 45.

In order to enable the machine to apply stay paper of various different widths as and when required, both the reel 37 and the guide member 39 are removable and replaceable by other reels and guide members designed to handle stay paper of the required different widths. The guide. member 39 has a base 68 are formed with return-bent flanges 71 which serve as guides for the lateral margins of the stay paper. Welded beneath the base 68 at its inlet end is a transverse sleeve 72 which, when the guide member is in position in the body 11, is adapted to receive a securing pin 73 (FIG. I) inserted through a hole ina lug 74 on the frame and also through a hole in a similar lug (not shown) on the other side of the sleeve 72.

In operation, a box blank 13 to be stayed is supported on a former block 9 is brought to rest by means (not illustrated) in the position shown in FIG. 1. Prior to this, a predetermined length 40' of stay paper will have been fed up close in front of the heat-sealing block 23. Air is now admitted into the pneumatic cylinder 14, as a result of which the piston (not shown) in the said cylinder causes the plunger I7 to advance in the direction towards the blank 13, taking with it the plate 22. the heat-sealing block 23, the housing 27 and the slotted knife 29. Since the stay paper is gripped between the feed roller 45 and the counter roller 47 and extends upwardly through the slot 35 in the slotted knife 29, the upwardly extending portion 40' will continue to be located close in front of the heat-sealing block I 23. Towards the end of the advance movement of the plunger 17, the Vee-notch 34 of the slotted knife 29 engages the corner of the former block 9 immediately below the corner 13' (FIG. 2) of the box blank 13, with the result that the slotted knife 29 is brought to rest. The heat-sealing block 23, however, continues to advance, so that cutting edges of the knife blade 28 cooperate with the cutting edges 36 of the slotted knife to sever the upwardly extending length 40' of stay paper. The stage at which this severing operation occurs is illustrated in FIG. 3 from which it will be seen that the upwardly extending length 40 of stay paper is, at the moment of severance, very close to the corner of the box blank 13. The distance between the length 40' of stay paper and the corner of the box blank at this moment is determined by the distance 74 (FIG. 5) between the angle of the Vee-notch 34 and the point where the cutting edges 36 meet. During the final part of the advance movement of the plunger 17 which brings the heat-sealing block 23 into the position shown in chain-dotted lines in FIG. 3, the length 40' of stay paper is secured under heat and pressure by the heat-sealing block to the vertical lower edge 13' FIG. 2) of the box blank. The Vee-groove 25 causes the stay paper to overlap the adjoining margins of the two side pieces of the blank 13 which meet at the corner edge 13. During the heat-sealing operation, the corrugations in the stay paper previously formed by the grooves in the roller 45 and the counter roller 47 are ironed out by the action of the heat-sealing block 23 as it presses the paper against the comer edge 13' of the blank 13.

Since the sliding bar 54 is held back by the spring 55 against the screw 52, it does not initially advance with the housing 27.

Consequently during an initial portion of theadvance movement of the housing 27, the toothed rack remains stationary, while the pinion 62 meshing with it rotates together with the plate 63, causing the. pawl 64 to ratchet over the ratchet wheel. At the end of this initial portion of the advance movement of the housing, the spindle 60 of the feed roller 45 engages the end of the slot 59 and thereafter the sliding bar 54 is drawn along with the housing 27 until the latter reaches the end of its advance movement. Thus, during the advance movement of the housing, the spindle 60 and the feed roller 45 carried thereby do not rotate.

After the length 40 of stay paper has been applied, a changeover valve (not shown) is operated so as to connect the interior of the pneumatic cylinder to the atmosphere. Thereupon, the plate 22,- the heat-sealing block 23 and housing 27 are returned by the springs towards the position shown in FIG. 1. During the initial part of this return movement, the springs 33 will cause the slotted knife to return to its initial position relative to the heat-sealing block 23. During a first part of the return movement, which includes this initial part, the action of the spring 55 will maintain the front end of the slot 59 in the sliding bar 54 in contact with the spindle 60. The sliding bar 54 will therefore move back during the first part of the return movement together with the housing 27 until its rear end engages the front end of the screw 52. During the remaining part of the return movement of the housing, the sliding bar 54 and the toothed rack 61 carried thereby remain stationary, with the result that the pinion 62 is rotated and drives the feed roller 45, via the plate 63, the pawl 64 and the ratchet wheel 65, causing a further length 40' of the stay paper 40' to be fed up through the slot 35 in the slotted knife 29. The vertical length of the piece 40' of stay paper which is fed up in this manner will depend upon the position in which the sliding bar 54 is brought to rest by the screw 52 and hence on the setting of the said screw, since the pinion 62 only rotates and drives the feed roller 45 during the last part of the return movement of the housing 27 after sliding bar 54 has engaged the screw 52.

The cycle of operations can how be repeated after the stayed box blank has been removed from the former block 9 and a fresh unstayed box blank 13 has been brought into the position shown in FIG. 1.

The staying unit described above is designed for staying the vertical corner edges of box blanks to produce box lids with a plain top or box bodies with a plain bottom. With one minor modification which will be described below with reference to FIG. 6, the unit can, however, be used for performing a similar staying operation on box blanks for the production of box lids with a flanged top or box bodies with a flanged bottom. The expression flanged top" used above in relation to a box lid means that the margins of the top wall of the lid project outwardly from the top edges of the side and end walls of the lid. Similarly the expression flanged bottom" used in relation to a box body means that the margins of the bottom wall of the body project outwardly from the side and end walls of the body.

Referring to FIG. 6, in which the various parts shown are designated by the same references as those which designate like parts in FIG. 1, it will be seen that the heat-sealing block 23 is formed with a cutout horizontal slot 23' to receive the comer portion of the projecting top flanges on the box blank 13. As shown in FIG. 7 the base of the slot 23' has inclined parts which are parallel to the corresponding surfaces of the vertical groove 25 in the heat-sealing block 23.

I claim:

1. In a box-making machine of the kind including:

a rectangular box former for supporting, one at a time, a succession of box blanks each having a middle portion which is to form the top or bottom of a box and flaps projecting from the edge of said middle portion;

means for bending the flaps of each blank with respect to the middle portion thereof to form sidewalls which, after being stayed, will form the corner edges ofa box;

the provision of a box-staying unit comprising:

a former block having a Vee-groove in its working face;

heating means for heating said former block;

' means for alternately advancing said former block towards,

and withdrawing it away from, a corner edge of each successive box blank supported on said box former;

stay-paper-feeding means operable by and during each withdrawal movement of the former block to advance the leading end of a continuous strip of stay paper through a predetermined distance across the working face of the former block in a direction parallel to the Vee-groove thereof so as to position a predetermined-length of stay paper for application under pressure and heat, during the next advance movement of the former block, to the corner edge of a box blank on the box former; and

stay-paper-severing means carried by said former block and arranged to be actuated, by engagement with the box former during the last part of each advance movement of said former block, to sever the previously positioned predetermined length of stay paper from the remainder of the continuous strip of stay paper.

2. A machine according to claim 1, wherein said stay-papersevering means includes:

an element arranged for axial sliding movement with respect to the former block in a direction parallel to the direction of movement of the latter and resiliently biased towards the box former; and

said axially slidable element being provided with a cutting edge adapted to cooperate with a cutting edge on the former block to sever said predetermined length of stay paper when said element is displaced by engagement with the box former.

3. A machine according to claim 2, wherein:

I the cutting edge on the former block is located at one end of, and flush with, the grooved working face of said former block;

the cutting edge on said axially slidable element extends along the front of a transverse slot in said axially slidable element; and

the stay-paper-feeding means is arranged to feed the staypaper through said transverse slot and thence across the working face of the former block.

4. A machine according to claim 3, wherein:

the transverse slot in said axially slidable element is Veeshaped with the line of symmetry of the Vee-coincident with the longitudinal centerline of that surface of said axially slidable element which contains the respective cutting edge; and the angle enclosed between the two limbs of the Vee being greaterthan'that between the walls of the Vee-shaped groove in-the working face of the former block. 5. A machine according to claim 1, wherein the stay-paperfeeding means comprises:

a stay-paper-feed roller; and a transmission drivably connected between said former block and said feed roller and including: a-one-way driving gear arranged to transmit the drive during withdrawal movements only of the former block; and an adjustable lost-motion device so arranged that, during a first part of each withdrawal movement of the former block having alength dependent upon the setting of said lost-motion device, lost motion is taken up by said lost-motion device and consequently no rotation is transmitted to said feed roller; and that, 7 during the remainder of said withdrawal movement, said:

former block is drivably connected through said oneway driving gear to rotate said feed roller and thereby feed up a predetermined length of stay paper proportional to the length of said remainder of said withdrawal movement of said former block.

6. A machine according to claim 5, wherein:

said box-staying unit has a stationary part;-

said feed roller is mounted on a shaft;

a stop'ismounted in said stationary part so as to be adjustable towards and away from said shaft;

said one-way driving gear includes a pinion input element thereof; and

said adjustable lost-motion device comprises: I i

a bar mounted for sliding movement in a stationary part of the box-staying unit and resiliently biased in the withdrawal direction of said former block;

a toothed rack fixed to said bar and meshing with said pinion; and

said bar being formed adjacent one end thereof witha longitudinal slot engaging over the shaft of the feed roller and having at its other end an abutment surfaceadapted to cooperate with said stop.

7. A machine according to claim 5, wherein said one-way driving gear includes:

a pawl-and-ratchet gear;

a rotatable plate carrying the pawl of said pawl-and-ratchet gear; and

said pinion is fixed for rotation with said rotatable plate.

8. A machine according to claim 5, wherein:

said box-staying unit has a stationary part; and

a slotted guide is removably mounted in said stationary part for guiding stay-paper to said stay-paper-feed roller.

which forms the 

1. In a box-making machine of the kind including: a rectangular box former for supporting, one at a time, a succession of box blanks each having a middle portion which is to form the top or bottom of a box and flaps projecting from the edge of said middle portion; means for bending the flaps of each blank with respect to the middle portion thereof to form sidewalls which, after being stayed, will form the corner edges of a box; the provision of a box-staying unit comprising: a former block having a Vee-groove in its working face; heating means for heating said former block; means for alternately advancing said former block towards, and withdrawing it away from, a corner edge of each successive box blank supported on said box former; stay-paper-feeding means operable by and during each withdrawal movement of the former block to advance the leading end of a continuous strip of stay paper through a predetermined distance across the working face of the former block in a direction parallel to the Vee-groove thereof so as to position a predetermined length of stay paper for application under pressure and heat, during the next advance movement of the former block, to the corner edge of a box blank on the box former; and stay-paper-severing means carried by said former block and arranged to be actuated, by engagement with the box former during the last part of each advance movement of said former block, to sever the previously positioned predetermined length of stay paper from the remainder of the continuous strip of stay paper.
 2. A machine according to claim 1, wherein said stay-paper-severing means includes: an element arranged for axial sliding movement with respect to the former block in a direction parallel to the direction of movement of the latter and resiliently biased towards the box former; and said axially slidable element being provided with a cutting edge adapted to cooperate with a cutting edge on the former block to sever said predetermined length of stay paper when said element is displaced by engagement with the box former.
 3. A machine according to claim 2, wherein: the cutting edge on the former block is located at one end of, and flush with, the grooved working face of said former block; the cutting edge on said axially slidable element extends along the front of a transverse slot in said axially slidable element; and the stay-paper-feeding means is arranged to feed the stay-paper through said transverse slot and thence across the working face of the former block.
 4. A machine according to claim 3, wherein: the transverse slot in said axially slidable element is Vee-shaped with the line of symmetry of the Vee-coincident with the longitudinal centerline of that surface of said axially slidable element which contains the respective cutting edge; and the angle enclosed between the two limbs of the Vee being greater than that between the walls of the Vee-shaped groove in the working face of the former block.
 5. A machine according to claim 1, wherein the stay-paper-feeding means comprises: a stay-paper-feed roller; and a transmission drivably connected between said former block and said feed roller and including: a one-way driving gear arranged to transmit the drive during withdrawal movements only of the former block; and an adjustable lost-motion device so arranged that, during a first part of each withdrawal movement of the former block having a length dependent upon the setting of said lost-motion device, lost motion is taken up by said lost-motion device and consequently no rotation is transmitted to said feed roller; and that, during the remainder of said withdrawal movement, said former bLock is drivably connected through said one-way driving gear to rotate said feed roller and thereby feed up a predetermined length of stay paper proportional to the length of said remainder of said withdrawal movement of said former block.
 6. A machine according to claim 5, wherein: said box-staying unit has a stationary part; said feed roller is mounted on a shaft; a stop is mounted in said stationary part so as to be adjustable towards and away from said shaft; said one-way driving gear includes a pinion which forms the input element thereof; and said adjustable lost-motion device comprises: a bar mounted for sliding movement in a stationary part of the box-staying unit and resiliently biased in the withdrawal direction of said former block; a toothed rack fixed to said bar and meshing with said pinion; and said bar being formed adjacent one end thereof with a longitudinal slot engaging over the shaft of the feed roller and having at its other end an abutment surface adapted to cooperate with said stop.
 7. A machine according to claim 5, wherein said one-way driving gear includes: a pawl-and-ratchet gear; a rotatable plate carrying the pawl of said pawl-and-ratchet gear; and said pinion is fixed for rotation with said rotatable plate.
 8. A machine according to claim 5, wherein: said box-staying unit has a stationary part; and a slotted guide is removably mounted in said stationary part for guiding stay-paper to said stay-paper-feed roller. 